1. Field of the Invention
The present invention relates to an ink jet printer, and, more particularly, to an ink jet cartridge system and corresponding method of printing using a plurality of same color inks with different intensities.
2. Description of the Related Art
Ink jet printers, in known manner, typically are used to jet a plurality of different color inks onto raster lines in an image area overlying a print medium to generate a print image on the print medium. Ink dots for each color ink are placed at corresponding pixel locations with a placement resolution which varies depending upon physical constraints associated with the printhead and/or hardware used to move the printhead across the print medium.
For a particular color ink, it is known to vary the effective density of the ink dots placed on the print medium to thereby affect the apparent shade of the ink. For a black ink. This process of altering the effective density is known as gray scale printing. One known method of gray scale printing is to divide the image area into a plurality of super pixels, with each super pixel including a plurality of respective individual pixels. By placing a selected number of ink dots at certain pixel locations within the super pixel, while leaving the remaining pixel locations blank, a gray scale image having a selected apparent shade can be generated. A problem with this method of gray scale printing is that, depending upon the number of blank pixel locations within the super pixel, the generated image may appear grainy to the human eye. This graininess may be objectionable depending upon the particular application for which the print image is generated.
Another known method of gray scale printing also uses a plurality of super pixels and places a single color ink at selected ink dot placement locations within the super pixels.
Additionally, however, the size (or diameter) of each individual ink dot may also be varied to affect the overall density of the single color ink within the super pixel. This method of printing may help alleviate the problem of graininess in the generated print image.
Yet another known method of gray scale printing uses a single cartridge with two different inks of a same color but different intensity therein. The same color but different intensity inks have been found to provide improved gray scale printing by changing the actual intensity or shade of the color ink, rather than changing the apparent density on the print image by altering the ink dot size and/or placement locations.
What is further needed in the art is a method of printing with an ink jet printer which provides a print image with an improved effective density or gray scale of a particular color ink in a print image on a print medium.